[Datetime-SIG] PEP 495 (Local Time Disambiguation) is ready for pronouncement

Ethan Furman ethan at stoneleaf.us
Tue Aug 18 21:09:32 CEST 2015

On 08/18/2015 11:41 AM, Alexander Belopolsky wrote:

> The problem with "hardcoding" the temporal relationship in the name of
>  the flag is that for a missing time `t` you get a counter-intuitive
> t.replace(later=True) - t.replace(later=False) < 0.

I don't understand this.  In the PEP it says:

> An instance that has first=False in a non-ambiguous case is said to represent
>  an invalid time (or is invalid for short), but users are not prevented from
>  creating invalid instances by passing first=False to a constructor or to a
>  replace() method.

and later

> The value of "first" will be ignored in all operations except those that
>  involve conversion between timezones.

So why won't `t.replace(_ltdf=True)` be the same value as `t.replace(_ltdf=False)` ?  The flag itself would be different, but the flag is not consulted for maths operations, right?


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